1. Field of the Invention
This invention relates to a fluorescence diagnosis system, and more particularly to a fluorescence diagnosis system in which the condition of a part of an organism to be diagnosed, e.g., change in the tissue condition of the part to be diagnosed, is recognized on the basis of auto fluorescence emitted from the tissue of the part to be diagnosed upon excitation by exciting light.
2. Description of the Related Art
There has been studied a fluorescence diagnosis system in which exciting light is projected onto a tissue of an organism, and auto fluorescence emitted from the tissue upon excitation by the exciting light is detected and analyzed, whereby change in the condition of the tissue caused by various diseases is recognized.
In the past, an attempt to recognize change in the tissue condition on the basis of change in intensity of the auto fluorescence was made. However since the intensity of the auto fluorescence has many sources of error and intensity information by itself does not sufficiently contribute to diagnosis, recently there have been made various attempts to recognize change in the tissue condition on the basis of the fact that the profile of spectral band intensities of the auto fluorescence changes with change in the tissue condition. For example, a diseased tissue greatly differs from a normal tissue in the ratio of intensity of a green region wavelength component of auto fluorescence to intensity of a red region wavelength component of the same. There has been proposed in Japanese Unexamined Patent Publication No. 6(1994)-54792 a fluorescence diagnosis system in which the ratio of intensity of a green region wavelength component to intensity of a red region wavelength component of auto fluorescence emitted from an organic tissue to be diagnosed is compared with that of an organic tissue which has been determined to be normal by a different system and whether the organic tissue to be diagnosed is diseased or normal is determined on the basis of the comparison. Further in the fluorescence diagnosis system disclosed in Japanese Unexamined Patent Publication No. 9(1997)-506027, intensities of auto fluorescence emitted from an organic tissue to be diagnosed at respective wavelengths are normalized with the intensity of the overall auto fluorescence (over the whole wavelength range) and made nondimensional, a difference curve is obtained by taking the difference between a profile curve of the nondimensional spectral band intensities and a similar profile curve for an organic tissue which has been determined to be normal by a different system (a reference profile curve), and whether the organic tissue to be diagnosed is diseased or normal is determined on the basis of the feature of the difference curve.
Further, we have proposed in Japanese Unexamined Patent Publication No. 10(1998)-225436 a fluorescence diagnosis system in which the intensity in a particular wavelength range of auto fluorescence emitted from an organic tissue to be diagnosed is normalized with the intensity of the overall auto fluorescence (over the whole wavelength range) and is compared with that of an organic tissue which has been determined to be normal by a different system, and whether the organic tissue to be diagnosed is diseased or normal is determined on the basis of comparison.
However, unlike a case where a sampled tissue is analyzed on a sample table by instruments, when living tissue is analyzed, the distance, angle and the like between the tissue and the part of the system from which the exciting light is projected onto the tissue and the auto fluorescence is received change from time to time. Accordingly characteristic of the detected auto fluorescence fluctuates, which makes it difficult to recognize change of the tissue condition (whether the tissue is normal or suffers from cancer, ulcer, inflammation, metaplasia or the like) at a reliable accuracy. Further the auto fluorescence also fluctuates depending on factors such as flow of blood which have little concern with the tissue condition. That is, since the auto fluorescence is very weak and includes various sources of error, it is very difficult to recognize change of a tissue at a high accuracy on the basis of a single characteristic value such as the intensity of the auto fluorescence or a normalized value of the intensity of the auto fluorescence.
In view of the foregoing observations and description, the primary object of the present invention is to provide a fluorescence diagnosis system which can recognize change of the part to be diagnosed at a high accuracy.
In accordance with the present invention, there is provided a fluorescence diagnosis system comprising an exciting light projecting means which projects onto an organic part to be observed exciting light which is in a predetermined wavelength range suitable for exciting intrinsic fluorophore of the organic part to emit auto fluorescence, a detecting means which detects the intensity of the auto fluorescence emitted from the intrinsic fluorophore of the organic part to be observed upon excitation by the exciting light, a characteristic value obtaining means which obtains a plurality of characteristic values from the intensity of the auto fluorescence detected by the detecting means, and a recognizing means which recognizes the condition of the organic part to be observed on the basis of the characteristic values.
For example, the characteristic values may comprise an intensity of the auto fluorescence and a normalized value of the intensity of the auto fluorescence, or a fluorescence yield of the auto fluorescence and a normalized value of the intensity of the auto fluorescence.
The normalized value of the intensity of the auto fluorescence may be obtained by dividing the intensity of a short wavelength component of the auto fluorescence by the intensity of the overall auto fluorescence.
For example, the recognizing means may recognize the condition of the organic part to be observed by making the characteristic values multivalued and executing a logical operation on the basis of the multivalued characteristic values.
Detection of the intensity of the auto fluorescence, obtaining the characteristic values and recognition of the condition of the organic part may be carried out pixel by pixel.
The expression xe2x80x9cfluorescence yieldxe2x80x9d means the ratio of the intensity of the exciting light projected onto the organic part to be diagnosed to the intensity of the auto fluorescence emitted from the organic part exposed to the exciting light.
In accordance with the present invention, since the tissue condition of the organic part to be observed is recognized on the basis of a plurality of characteristic values obtained from the intensity of the auto fluorescence, the tissue condition can be recognized at a higher accuracy, irrespective of change of the auto fluorescence due to change in the distance, angle and the like between the tissue and the part of the system from which the exciting light is projected onto the tissue and the auto fluorescence is received or due to factors such as flow of blood which have little concern with the tissue condition, as compared with the conventional fluorescence diagnosis system where the tissue condition is recognized on the basis of a single characteristic value.
When the characteristic values comprise an intensity of the auto fluorescence and a normalized value of the intensity of the auto fluorescence, or a fluorescence yield of the auto fluorescence and a normalized value of the intensity of the auto fluorescence, the characteristic values can more properly reflect the tissue condition of the organic part and the tissue condition can be recognized at a further higher accuracy.
In this case, when the normalized value of the intensity of the auto fluorescence is obtained by dividing the intensity of a short wavelength component of the auto fluorescence by the intensity of the overall auto fluorescence, the characteristic values can further more properly reflect the tissue condition of the organic part and the tissue condition can be recognized at a further higher accuracy.
When the recognizing means recognizes the condition of the organic part to be observed by making the characteristic values multivalued and executing a logical operation on the basis of the multivalued characteristic value, the operation for recognizing the tissue condition is simplified and the time required to recognize the tissue condition is shortened.